Enzymatic enrichment of acylglycerols rich in n - 3 polyunsaturated fatty acids by selective methanolysis: Optimization and kinetic studies.

n - 3 Polyunsaturated fatty acids (n - 3 PUFA) have special physiological effect, but their contents in natural oils may not meet the growing demand. Lipase-catalyzed selective methanolysis could be used to produce acylglycerols rich in n - 3 PUFA. To explore the kinetics of enzymatic methanolysis, factors affecting the reaction, including reaction system, water content, substrate molar ratio, temperature, lipase loading, and reaction time, were first investigated in the view of optimizing the reaction. Then the effects of triacylglycerol concentrations and methanol concentrations on initial reaction rate were studied. Finally, the key kinetic parameters of methanolysis were determined subsequently. The results showed that under optimal conditions, the n - 3 PUFA content in acylglycerols increased from 39.88% to 71.41%, and the n - 3 PUFA yield was 73.67%. The reaction followed a Ping-Pong Bi Bi mechanism with inhibition by methanol. The kinetic analysis indicated the lipase could selectively remove saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) in acylglycerols. The inhibition constant of methanol to the n - 3 PUFA (K , 0.30 mmol/L) was lower than that to the SFA and MUFA (219.64 and 79.71 mmol/L). The combined effects of the fatty acid selectivity of Candida antarctica lipase A and methanol inhibition resulted in an enrichment of n - 3 PUFA in acylglycerols. Overall, the methanolysis reaction catalyzed by the lipase A is a prospective enrichment method. PRACTICAL APPLICATION: This study demonstrated that enzymatic selective methanolysis is a prospective enrichment method to produce acylglycerols rich in n - 3 PUFA. This method is highly efficient, environment-friendly, and simple. n - 3 PUFA concentrates have been widely applied in the food, health-care food, and pharmaceutical industries.